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So you're going to a school (which I assume you've paid for), to learn about cryptography - only to be told "don't ever bother"?

hannob 5y ago
Of course at some point some people will have to implement crypto. But I think a good way to think about it is this: This shouldn't be on top of your list when you learn crypto. Before you even think about rolling your own crypto you should break other people's crypto. That'll help you to gain deeper insights in how the whole thing works. (Disclaimer: I broke other people's crypto, I wrote papers about it. I still never tried to roll my own crypto.)
lucb1e 5y ago
That's how it always felt for me, yeah. At peak, and in multiple independent courses, the teacher would step through a well-made AES key schedule visualization while none of us are (even planning on) doing the heavy math studies necessary to design a successor to or find vulnerabilities in something like AES. Most of us would be software engineers, sysadmins, or perhaps a handful of us might go into security fields like forensics or pentesting. The internals of AES are completely irrelevant. A curiosity maybe, but not something to be quizzed on. Then I went to do my master's and the teacher started about caesar ciphers... All formal cryptography-for-non-cryptographers education I've ever had was completely useless (I was in tertiary education in the Netherlands between 2010 and 2018, in case anyone is wondering how dated this is). The concept of authenticated encryption was mentioned in passing I think, though in one course I had to prompt the teacher to mention that as what you would want to be doing, but got far less attention or practice than doing things like a Caesar cipher or AES key schedule by hand. Merely knowing that you have to look for the keyword authenticated encryption (when you want to do encryption for some reason) would already be enough in my opinion, from there you can find good answers. Or for secure connections, keyword searches should include something about key distribution/verification and, if you want to use something configurable like TLS, also configuration choices like enforcing allowed protocol versions. Which versions those are, that changes over time and there is little point memorizing it. You should just know that you should look into this when you need it.

hannob 5y ago

Of course at some point some people will have to implement crypto. But I think a good way to think about it is this: This shouldn't be on top of your list when you learn crypto. Before you even think about rolling your own crypto you should break other people's crypto. That'll help you to gain deeper insights in how the whole thing works. (Disclaimer: I broke other people's crypto, I wrote papers about it. I still never tried to roll my own crypto.)

lucb1e 5y ago

That's how it always felt for me, yeah. At peak, and in multiple independent courses, the teacher would step through a well-made AES key schedule visualization while none of us are (even planning on) doing the heavy math studies necessary to design a successor to or find vulnerabilities in something like AES. Most of us would be software engineers, sysadmins, or perhaps a handful of us might go into security fields like forensics or pentesting. The internals of AES are completely irrelevant. A curiosity maybe, but not something to be quizzed on. Then I went to do my master's and the teacher started about caesar ciphers... All formal cryptography-for-non-cryptographers education I've ever had was completely useless (I was in tertiary education in the Netherlands between 2010 and 2018, in case anyone is wondering how dated this is). The concept of authenticated encryption was mentioned in passing I think, though in one course I had to prompt the teacher to mention that as what you would want to be doing, but got far less attention or practice than doing things like a Caesar cipher or AES key schedule by hand. Merely knowing that you have to look for the keyword authenticated encryption (when you want to do encryption for some reason) would already be enough in my opinion, from there you can find good answers. Or for secure connections, keyword searches should include something about key distribution/verification and, if you want to use something configurable like TLS, also configuration choices like enforcing allowed protocol versions. Which versions those are, that changes over time and there is little point memorizing it. You should just know that you should look into this when you need it.